The Internet, and especially the World Wide Web (“web”), has made vast amounts of information available to users through their Internet browsers. Although this information is easily accessible to users, there is so much information that it presents problems as users try to identify what information is relevant to their needs. This problem has been referred to as the information explosion problem. Search engine services have been developed to help users find information that is relevant to their needs. These search engine services allow users to search for display pages, such as web pages, that may be of interest to users. After a user submits a search request (i.e., a query) that includes search terms, the search engine service identifies web pages that may be related to those search terms. To quickly identify related web pages, the search engine services may maintain a mapping of keywords to web pages. This mapping may be generated by crawling the web to identify the keywords of each web page. To crawl the web, a search engine service may use a list of root web pages to identify all web pages that are accessible through those root web pages. The keywords of any particular web page can be identified using various well-known information retrieval techniques, such as identifying the words of a headline, the words supplied in the metadata of the web page, the words that are highlighted, and so on. The search engine service identifies web pages that may be related to the search request based on how well the keywords of a web page match the words of the query. The search engine service then displays to the user links to the identified web pages in an order that is based on a ranking that may be determined by their relevance to the query, popularity, importance, and/or some other measure.
While such general approaches to searching for information of interest are useful in many situations, they may present problems in certain situations. One such situation occurs when a person who is a native speaker of one language is looking for help when writing in another language. For example, a person who is native speaker of Chinese and who is writing a document in English may find it difficult to identify the most appropriate English word to express their intent. Although the person could submit a query to a search engine service to retrieve web pages with sentences that may provide some help in determining the appropriate word, the person may not even know any English words that are similar in meaning, which makes keyword searching difficult. For example, if the person wants to express that they are happy with life, the person may know that the sentence should have the words “I” and “life,” but may not know that the words “enjoy” and “like” might be appropriate words for forming the sentences “I enjoy life” or “I like life.” If the person submitted the query “I life” to a search engine service, the search results are likely to include references relating to an “iLife” software product, a definition of “life,” life-skills training, and so on. Such results, however, are unlikely to include sample sentences that would help the person identify an appropriate word for expressing their meaning.
Another situation occurs when a person is searching for documents relating to a certain topic, but with a simple series of keywords that might not accurately express their intention. For example, a person who is researching sources of revenue for a governmental entity may want to compile a list of common names for different types of taxes, such as income tax, real estate tax, death tax, vehicle tax, sales tax, and so on. The person may submit the query “common names of taxes,” which would seem to accurately describe the interest of the person. In that instance, search engine services are likely to return documents related to name and tax issues relating to common law marriages, a book on common and scientific names that is for sale at a price that includes tax, and so on. Such documents, however, would not be of interest to the person interested in the common names of taxes.